A clean procedure for the synthesis of 1,4-dihydropyridines via Hantzsch reaction in water

A clean and efficient procedure was established to synthesize 1,4-dihydropyridines via one-pot Hantzsch reactions in aqueous medium without the use of a catalyst and/or organic solvent. The reaction with stoichiometric molar ration could be carried out in a sealed vessel with a water steam, air, or nitrogen atmosphere to afford Hantzsch esters in good to excellent yields and purities. After the simple filtration, the 1,4-dihydropyridines were isolated, and the filtrate could be recycled and reused without significantly decreasing the yields and purities. The novel and clean methodology offers the advantages including short reaction time, good yields, operational simplicity, less leaks, and environmentally benign.